-http mode exit doesn't exit

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ralph.ronnquist
Posts: 216
Joined: Mon Jun 02, 2014 1:40 am
Location: Melbourne, Australia

-http mode exit doesn't exit

Post by ralph.ronnquist »

When tracking down why my ^C handler

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(signal 2 exit)
made newlisp in -http mode crash rather then exit, I found that p_exit doesn't actually exit in daemonMode, but rather it IOchannel=0 and throws (aka longjmps) an ERR_USER_RESET error. Thus, execution eventually continues at the AFTER_ERROR_ENTRY label, where fileno stubbornly objects to the IOchannel==0 by crashing. On Linux.

I'm not sure about the intention with p_exit not actually exiting in daemonMode.

Assuming there's a good reason for it, one should avoid IOchannel=0 to let the service progress as per normal. Though, then it's seriously hard to make it exit; either import my own exit or, not so gracefully, rely on (/ 0 0).

Lutz
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Re: -http mode exit doesn't exit

Post by Lutz »

Yes, this is how it is supposed to work. The -d demon mode will only exit/close the current connection, reset newLISP by rolling back stacks and set the evaluation level to top, then listen again for a new connection (1). The top level variable environment state is kept, e.g. when setting a global (top level) variable or definition, exiting and reconnecting again, that variable or definition has the same value.

If you want the server exit for real, use -p instead of -d.

See also:
http://www.newlisp.org/downloads/newlis ... pip_server
and:
http://www.newlisp.org/downloads/newlis ... tml#daemon

(1) Setting IOchannel=NULL is just part of the procedure to force a restart of the server after the reset(). setupServer() then reconfigures IOchannel to a valid Unix file descriptor.

ps: you also could do

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(destroy (sys-info -3))
.. if you must.

ralph.ronnquist
Posts: 216
Joined: Mon Jun 02, 2014 1:40 am
Location: Melbourne, Australia

Re: -http mode exit doesn't exit

Post by ralph.ronnquist »

Fair enough. exit is supposed to mean "exit the session" rather than "exit the program". Maybe I should read the manual sometimes ;-)

Then I suppose something needs to be done about fileno crashing on IOchannel==0, which sometimes exits the program anyhow with core dump or continues after signaling memory corruption error etc.

The destroy option is good. Though it kills via a new signal, so I'll probably go for importing the "raw" exit instead, as it really is far too easy to grumble about.

ralph.ronnquist
Posts: 216
Joined: Mon Jun 02, 2014 1:40 am
Location: Melbourne, Australia

Re: -http mode exit doesn't exit

Post by ralph.ronnquist »

Actually, crashing only seems to happen without open connection.

Calling exit with a connection open closes the connection and doesn't crash.

But it then also stops invoking the handler (the low level signal_handler is no longer invoked). This would be because signal_handler doesn't return, which leaves the signal in blocked state. Maybe the signal setup should use sigaction rather than signal, and set up the handling with a SA_NODEFER flag, which avoids that blocking?

Thus:
1) signal handling calling exit without open connection leads to crash, and
2) signal handling calling exit with open connection makes the signal subsequently blocked.

Basically, calling exit in a signal handler for a daemon mode script is a bad idea. I suppose calling reset in a signal handler would be a problem regardless of mode.

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